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Message-ID: <282e3f4f-c3ef-4b42-bf9e-3a1ab25a8091@huawei.com>
Date: Wed, 25 Sep 2024 21:31:58 +0800
From: Yonglong Liu <liuyonglong@...wei.com>
To: Yunsheng Lin <linyunsheng@...wei.com>, <davem@...emloft.net>,
<kuba@...nel.org>, <pabeni@...hat.com>
CC: <fanghaiqing@...wei.com>, <zhangkun09@...wei.com>, Alexander Lobakin
<aleksander.lobakin@...el.com>, Robin Murphy <robin.murphy@....com>,
Alexander Duyck <alexander.duyck@...il.com>, IOMMU <iommu@...ts.linux.dev>,
Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend
<john.fastabend@...il.com>, Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
<netdev@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>,
<bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH net v2 0/2] fix two bugs related to page_pool
Tested-by: Yonglong Liu <liuyonglong@...wei.com>
On 2024/9/25 15:57, Yunsheng Lin wrote:
> Patch 1 fix a possible time window problem for page_pool.
> Patch 2 fix the kernel crash problem at iommu_get_dma_domain
> reported in [1].
>
> When page_pool_put_unrefed_netmem() is called with allow_direct
> being true, there is only a newly added checking overhead
> introduced in patch 1, which seem to be no noticeable performance
> impact.
>
> When page_pool_put_unrefed_netmem() is called with allow_direct
> being false, there is an added rcu read lock overhead introduced in
> patch 1, and the overhead is about 13ns using the below test code,
> but 'time_bench_page_pool02_ptr_ring' only show about 2ns overhead,
> which is about 2% degradation.
>
> +static int time_bench_rcu(
> + struct time_bench_record *rec, void *data)
> +{
> + uint64_t loops_cnt = 0;
> + int i;
> +
> + time_bench_start(rec);
> + /** Loop to measure **/
> + for (i = 0; i < rec->loops; i++) {
> + rcu_read_lock();
> + loops_cnt++;
> + barrier(); /* avoid compiler to optimize this loop */
> + rcu_read_unlock();
> + }
> + time_bench_stop(rec, loops_cnt);
> + return loops_cnt;
> +}
>
> When page_pool need to be refilled from or flushed to the page allocator,
> the added overhead is the page_pool_item_add() and page_pool_item_del()
> calling overhead, using below patch to enable Jesper's testing running in
> arm64, the overhead is 0~20ns, which is quite variable
>
> Before this patchset:
> root@(none)$ taskset -c 1 insmod bench_page_pool_simple.ko
> [ 136.641453] bench_page_pool_simple: Loaded
> [ 136.722560] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076968720 sec time_interval:76968720) - (invoke count:100000000 tsc_interval:7696855)
> [ 137.317006] time_bench: Type:atomic_inc Per elem: 0 cycles(tsc) 5.771 ns (step:0) - (measurement period time:0.577164350 sec time_interval:577164350) - (invoke count:100000000 tsc_interval:57716429)
> [ 137.480852] time_bench: Type:lock Per elem: 1 cycles(tsc) 14.621 ns (step:0) - (measurement period time:0.146218730 sec time_interval:146218730) - (invoke count:10000000 tsc_interval:14621868)
> [ 138.842377] time_bench: Type:rcu Per elem: 1 cycles(tsc) 13.444 ns (step:0) - (measurement period time:1.344419820 sec time_interval:1344419820) - (invoke count:100000000 tsc_interval:134441975)
> [ 138.859656] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path
> [ 139.132102] time_bench: Type:no-softirq-page_pool01 Per elem: 2 cycles(tsc) 26.315 ns (step:0) - (measurement period time:0.263151430 sec time_interval:263151430) - (invoke count:10000000 tsc_interval:26315135)
> [ 139.150769] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path
> [ 139.910642] time_bench: Type:no-softirq-page_pool02 Per elem: 7 cycles(tsc) 75.066 ns (step:0) - (measurement period time:0.750663200 sec time_interval:750663200) - (invoke count:10000000 tsc_interval:75066312)
> [ 139.929312] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path
> [ 141.673951] time_bench: Type:no-softirq-page_pool03 Per elem: 17 cycles(tsc) 173.578 ns (step:0) - (measurement period time:1.735781610 sec time_interval:1735781610) - (invoke count:10000000 tsc_interval:173578155)
> [ 141.692970] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path
> [ 141.700874] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path
> [ 141.973638] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 2 cycles(tsc) 26.364 ns (step:0) - (measurement period time:0.263645150 sec time_interval:263645150) - (invoke count:10000000 tsc_interval:26364508)
> [ 141.992912] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path
> [ 142.531745] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 5 cycles(tsc) 52.980 ns (step:0) - (measurement period time:0.529801250 sec time_interval:529801250) - (invoke count:10000000 tsc_interval:52980119)
> [ 142.550933] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path
> [ 144.297646] time_bench: Type:tasklet_page_pool03_slow Per elem: 17 cycles(tsc) 173.802 ns (step:0) - (measurement period time:1.738029000 sec time_interval:1738029000) - (invoke count:10000000 tsc_interval:173802894)
>
> After this patchset:
> root@(none)$ taskset -c 1 insmod bench_page_pool_simple.ko
> [ 149.865799] bench_page_pool_simple: Loaded
> [ 149.946907] time_bench: Type:for_loop Per elem: 0 cycles(tsc) 0.769 ns (step:0) - (measurement period time:0.076965620 sec time_interval:76965620) - (invoke count:100000000 tsc_interval:7696556)
> [ 150.722282] time_bench: Type:atomic_inc Per elem: 0 cycles(tsc) 7.580 ns (step:0) - (measurement period time:0.758094660 sec time_interval:758094660) - (invoke count:100000000 tsc_interval:75809459)
> [ 150.886335] time_bench: Type:lock Per elem: 1 cycles(tsc) 14.640 ns (step:0) - (measurement period time:0.146405830 sec time_interval:146405830) - (invoke count:10000000 tsc_interval:14640578)
> [ 152.249454] time_bench: Type:rcu Per elem: 1 cycles(tsc) 13.460 ns (step:0) - (measurement period time:1.346009570 sec time_interval:1346009570) - (invoke count:100000000 tsc_interval:134600951)
> [ 152.266734] bench_page_pool_simple: time_bench_page_pool01_fast_path(): Cannot use page_pool fast-path
> [ 152.537046] time_bench: Type:no-softirq-page_pool01 Per elem: 2 cycles(tsc) 26.100 ns (step:0) - (measurement period time:0.261007670 sec time_interval:261007670) - (invoke count:10000000 tsc_interval:26100761)
> [ 152.555714] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): Cannot use page_pool fast-path
> [ 153.342212] time_bench: Type:no-softirq-page_pool02 Per elem: 7 cycles(tsc) 77.729 ns (step:0) - (measurement period time:0.777293380 sec time_interval:777293380) - (invoke count:10000000 tsc_interval:77729331)
> [ 153.360881] bench_page_pool_simple: time_bench_page_pool03_slow(): Cannot use page_pool fast-path
> [ 155.287747] time_bench: Type:no-softirq-page_pool03 Per elem: 19 cycles(tsc) 191.800 ns (step:0) - (measurement period time:1.918007990 sec time_interval:1918007990) - (invoke count:10000000 tsc_interval:191800791)
> [ 155.306766] bench_page_pool_simple: pp_tasklet_handler(): in_serving_softirq fast-path
> [ 155.314670] bench_page_pool_simple: time_bench_page_pool01_fast_path(): in_serving_softirq fast-path
> [ 155.584313] time_bench: Type:tasklet_page_pool01_fast_path Per elem: 2 cycles(tsc) 26.052 ns (step:0) - (measurement period time:0.260524810 sec time_interval:260524810) - (invoke count:10000000 tsc_interval:26052476)
> [ 155.603588] bench_page_pool_simple: time_bench_page_pool02_ptr_ring(): in_serving_softirq fast-path
> [ 156.183214] time_bench: Type:tasklet_page_pool02_ptr_ring Per elem: 5 cycles(tsc) 57.059 ns (step:0) - (measurement period time:0.570594850 sec time_interval:570594850) - (invoke count:10000000 tsc_interval:57059478)
> [ 156.202402] bench_page_pool_simple: time_bench_page_pool03_slow(): in_serving_softirq fast-path
> [ 158.045594] time_bench: Type:tasklet_page_pool03_slow Per elem: 18 cycles(tsc) 183.450 ns (step:0) - (measurement period time:1.834507700 sec time_interval:1834507700) - (invoke count:10000000 tsc_interval:183450764)
>
> Patch for time_bench.h enable the out of tree testing on arm64 system:
> @@ -101,6 +101,7 @@ struct time_bench_cpu {
> * CPUID clears the high 32-bits of all (rax/rbx/rcx/rdx)
> */
> static __always_inline uint64_t tsc_start_clock(void) {
> +#if defined(__i386__) || defined(__x86_64__)
> /* See: Intel Doc #324264 */
> unsigned hi, lo;
> asm volatile (
> @@ -111,9 +112,13 @@ static __always_inline uint64_t tsc_start_clock(void) {
> "%rax", "%rbx", "%rcx", "%rdx");
> //FIXME: on 32bit use clobbered %eax + %edx
> return ((uint64_t)lo) | (((uint64_t)hi) << 32);
> +#else
> + return get_cycles();
> +#endif
> }
>
> static __always_inline uint64_t tsc_stop_clock(void) {
> +#if defined(__i386__) || defined(__x86_64__)
> /* See: Intel Doc #324264 */
> unsigned hi, lo;
> asm volatile(
> @@ -123,6 +128,9 @@ static __always_inline uint64_t tsc_stop_clock(void) {
> "CPUID\n\t": "=r" (hi), "=r" (lo)::
> "%rax", "%rbx", "%rcx", "%rdx");
> return ((uint64_t)lo) | (((uint64_t)hi) << 32);
> +#else
> + return get_cycles();
> +#endif
> }
>
> /* Notes for RDTSC and RDTSCP
> @@ -186,10 +194,14 @@ enum {
>
> static __always_inline unsigned long long p_rdpmc(unsigned in)
> {
> +#if defined(__i386__) || defined(__x86_64__)
> unsigned d, a;
>
> asm volatile("rdpmc" : "=d" (d), "=a" (a) : "c" (in) : "memory");
> return ((unsigned long long)d << 32) | a;
> +#else
> + return 0;
> +#endif
> }
>
> /* These PMU counter needs to be enabled, but I don't have the
> @@ -216,7 +228,11 @@ static __always_inline unsigned long long pmc_clk(void)
> #define MSR_IA32_PCM2 0x400000C3
> inline uint64_t msr_inst(unsigned long long *msr_result)
> {
> +#if defined(__i386__) || defined(__x86_64__)
> return rdmsrl_safe(MSR_IA32_PCM0, msr_result);
> +#else
> + return 0;
> +#endif
> }
>
> 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel.org/T/
>
> CC: Alexander Lobakin <aleksander.lobakin@...el.com>
> CC: Robin Murphy <robin.murphy@....com>
> CC: Alexander Duyck <alexander.duyck@...il.com>
> CC: IOMMU <iommu@...ts.linux.dev>
>
> Change log:
> V2:
> 1. Add a item_full stat.
> 2. Use container_of() for page_pool_to_pp().
>
> Yunsheng Lin (2):
> page_pool: fix timing for checking and disabling napi_local
> page_pool: fix IOMMU crash when driver has already unbound
>
> drivers/net/ethernet/freescale/fec_main.c | 8 +-
> drivers/net/ethernet/intel/iavf/iavf_txrx.c | 6 +-
> drivers/net/ethernet/intel/idpf/idpf_txrx.c | 14 +-
> drivers/net/ethernet/intel/libeth/rx.c | 2 +-
> .../net/ethernet/mellanox/mlx5/core/en/xdp.c | 3 +-
> drivers/net/netdevsim/netdev.c | 6 +-
> drivers/net/wireless/mediatek/mt76/mt76.h | 2 +-
> include/linux/mm_types.h | 2 +-
> include/linux/skbuff.h | 1 +
> include/net/libeth/rx.h | 3 +-
> include/net/netmem.h | 10 +-
> include/net/page_pool/helpers.h | 7 +
> include/net/page_pool/types.h | 17 +-
> net/core/devmem.c | 4 +-
> net/core/netmem_priv.h | 5 +-
> net/core/page_pool.c | 190 +++++++++++++++---
> net/core/page_pool_priv.h | 10 +-
> net/core/skbuff.c | 3 +-
> net/core/xdp.c | 3 +-
> 19 files changed, 238 insertions(+), 58 deletions(-)
>
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